1. Field of the Invention
The present invention relates to an oscillating motor, and more particularly, to an oscillating motor in which a concave portion and a convex portion are formed at the inner circumferential surface of a rotor and a stator to increase contact area, thereby increasing a torque of the motor, and an AC power applied to the motor is controlled to variably control the area where the rotor is reciprocally rotated, thereby increasing an efficiency of a compressor.
2. Description of the Background Art
In general, a motor controls an operation of a switching device to switch on or off a power supplied to a coil wound on a multi-phase stator, so as to generate a rotational torque. As the excitation state of the rotor and the stator of the motor is sequentially varied, a forward directional rotational torque is generated thanks to the generated magnetic suction force, and if a specific excitation state between the rotor and the stator of the motor is not varied, the rotor is stopped at a certain position.
In addition, by controlling a phase of an input pulse signal applied to the switching device with formation of the maximum inductance of the motor as the starting point, a reverse-rotational force is generated, and accordingly, the motor can be controlling in its driving and direction.
The construction of the motor will now be described with reference to FIG. 1.
FIG. 1 is a sectional view showing a structure of a motor in accordance with a conventional art.
As shown in FIG. 1, the motor includes a cylindrical stator 13, a rotor 11 rotatably inserted at the inner side, a rotational shaft 10 provided at the center of the rotor 11 as an output shaft, stator teeth 14, a coil 15 wound on the stator teeth, a position detecting unit (not shown) for detecting a position of the rotor, and a controller (not shown) for controlling the motor according to a position detected by the position detecting unit.
The stator 13 includes six teeth 14 formed protruded at a certain angle (60° at the inner side of the mother body. The coil 15 is wound at each of the stator teeth 14, making stator poles. The stator poles are electrically connected to each other in the diagonal direction, to form 3 phases (a, b, c) that the same polarity is generated.
The rotor 11 includes four rotor teeth 12 formed protruded at a certain angle, that is, at a 90°, on the outer circumferential surface. The rotor teeth 12 is rotated with a void formed with an end portion of the stator teeth 14.
As an embodiment of the above-constructed motor, an SRM motor will now be described.
FIG. 2 is a circuit diagram showing the construction of the SRM motor in accordance with the conventional art.
As shown in FIG. 2, the SRM motor includes a DC link capacitor (C) 26 for smoothing an inputted voltage and supplying the resulted DC voltage to switched reluctance motor (SRM) motor, coils 27, 28 and 29 of the ‘N’ number of motors respectively connected in parallel as many as the number of ‘N’ phases, upper switch devices 20, 22 and 24 and lower switch devices 30, 31 and 32 connected in series vertically to the coils 27, 28 and 29 of the motor, free wheel diodes 33, 34 and 35 connected between an emitter of the upper switch devices 20, 22 and 24 and an emitter of the lower switch devices 30, 31 and 32, and free-wheel diodes 21, 23 and 25 connected between a collector of the upper switch devices 20, 22 and 24 and the emitter of the lower switch devices 30, 31 and 32.
The operation of the SRM motor will now be described in detail with reference to FIGS. 1, 2 and 3A through 3C.
FIGS. 3A through 3C show waveforms of periods to control the speed of the motor under the dwell control in accordance with the conventional art.
As shown in FIGS. 3A through 3C, the position detecting unit detects a position of the rotor teeth 12 and outputs a position detection pulse to the rotor 11. Then, the stator 13 synchronizes the position detection pulse, applies a current to the 3 phases (a, b, c) excitation coil 15 and generates an electromagnetic force.
That is, when a voltage is inputted to the DC link capacitor 26, the DC link capacitor 26 smoothes the inputted voltage and applies it to the SRM motor.
Upon receipt of the smoothed voltage, that is, the DC voltage, the SRM motor is rotated, and by installing a motor interrupter and a disk having a slog related to each phase in the motor, the position of the rotor is detected by the photo sensor.
After the position of the rotor is detected, when the motor is operated at a low speed, as shown in FIG. 3A, the period of the gate signal (ga) for controlling the switch device of the motor is made shortened to control the current applied to the motor.
In case that the motor is operated at a middle speed, the switch device of the motor is controlled with a signal period as shown in FIG. 3B, and in case that the motor is operated at a high speed, the switch device of the motor is controlled with a signal period as shown in FIG. 3C, whereby the current flowing to the motor is controlled to rotate the motor in the forward direction or in the backward direction.
In the method for controlling the 3 phases of stator coils by the dwell time, the case that the motor is operated at a low speed will now be described in detail.
In order to generate electricity at the phase ‘1’ of the stator coil and generate an electromagnetic force, a high level of phase ‘a’ gate signal (ga) is supplied to a gate of the upper and the lower switch devices 20 and 30 connected in series to the motor coil 27. When the upper and the lower switch devices 20 and 33 of the phase ‘a’ are turned on by the high level of gate signal as supplied, a current flows to the motor coil 27 connected in series to the upper and the lower switch device, so that electricity is generated at the motor coil 27 of the phase ‘a’.
After electricity is generated at the motor coil 27 of the phase ‘a’ and the current flows to the motor coil 27 of the phase ‘a’ for a predetermined dwell time (T), a low level of gate signal (ga) is outputted to the upper and the lower switch devices 20 and 30.
When the low level signal is outputted, the upper and lower switch devices 20 and 30 are simultaneously turned on off and the magnetic flux generated at the motor coil 27 of the phase ‘a’ is removed while passing the DC link capacitor 26 and the motor coil 27, so that that motor is smoothly rotated.
In case that an electromagnetic force is generated at the stator coil ‘b’, in order generate electricity at the stator coil, the high level gate signal (gb) of the phase ‘b’ is supplied to the gate of the upper and lower switch devices 22 and 31 connected in series to the motor coil 28, and accordingly, the upper and lower switch devices 22 and 31 of the phase ‘b’ are simultaneously turned on.
As the upper and lower switch devices 22 and 31 of the phase ‘b’ are turned on, the current flows to the motor coil 28, and thus, electricity can be generated at the motor coil 28 of the phase ‘b’.
When the electricity is generated at the motor coil 28 of the phase ‘b’, the current flows for a predetermined dwell time, and then the low level of gate signal (ga) is outputted to the upper and lower switch devices 22 and 31.
When the low level signal is outputted, the upper and lower switch devices 22 and 31 are simultaneously turned off, and the magnetic flux generated at the coil 28 of the motor of the phase ‘b’ is removed by the free wheel diodes 23 and 34, the DC link capacitor 26 and the motor coil 28, so that the motor can be smoothly rotated.
In case of the phase ‘c’, it also has the same operations as those of the phases ‘a’ and ‘b’, thus, descriptions are omitted.
When current is applied to the stator 13 and the motor is rotated, a microcomputer detects a position of the rotor by means of the position detecting unit and controls switching of the plurality of switch devices 20, 22, 24, 30, 31, and 32, according to which the motor is rotated in the forward direction or the backward direction.
However, as described above, though the motor can be rotated at a high speed in the forward or in the backward direction, it is incapable of making a reciprocal rotational movement at a high speed in a certain area. Therefore, it fails to be adoptable to a mechanism or a device which needs a high-speed reciprocal movement. In addition, if it is possibly adoptable, a conversion mechanism for changing a rotational movement to a linear movement is to be additionally installed, causing a problem that its expense is increased.